Method and device to deghost seismic data

Abstract

A method for processing seismic data related to a structure under a body of water to generate an image of the structure includes receiving seismic data acquired using detectors disposed on a depth-varying profile streamer. The method further includes generating, from the seismic data, first traces that correspond to traces as recorded by the detectors and migrated to water surface, and second traces that correspond to traces as would be recorded by virtual detectors mirroring the detectors relative to the water surface and migrated to water surface. The method also includes generating third traces as a sum of corresponding ones among the first traces and second traces, and fourth traces as a difference of the corresponding ones of the first and second traces. The method then includes deghosting at least one of the first and second traces using positive and negative polarity portions of the third and fourth traces.

Description

BACKGROUND[0001]1. Technical Field[0002]Embodiments of the subject matter disclosed herein generally relate to methods and systems configured to process marine seismic data, including a fast deghosting of variable-depth streamer data.[0003]2. Discussion of the Background[0004]Since the 1980s, reflection seismology has become more and more important in oil and gas industry for mapping and interpreting underground or under sea-bottom geophysical structure, to identify potential oil and / or gas reservoirs.[0005]Marine seismic surveys for acquiring reflection seismic data are conducted using specially-equipped vessels that tow (A) seismic sources such as air-gun arrays that generate waves directed to the subsurface, and (B) cables (named streamers) containing detectors such as hydrophones and geophones that detect reflected waves. The reflected waves are due to the source-generated waves being reflected from seismic interfaces (i.e., where there is a lithological variation or change).[00...

AI Technical Summary

Benefits of technology

The patent describes a method and apparatus for processing seismic data to create an image of a structure underwater. The method involves generating first traces from the seismic data, which are the signals recorded by detectors on a depth-varying profile streamer. These first traces are then combined with second traces, which are the signals that would be recorded by virtual detectors mirroring the first traces. The resulting combination of signals is then used to create an image of the structure. The method also includes deghosting the first and second traces using positive and negative polarity portions of the third and fourth traces to improve the signal-to-noise ratio and create a better image. The technical effect of this patent is to provide a more accurate and reliable method for processing seismic data to create an image of a structure underwater.

Problems solved by technology

However, towing the detectors below the water surface introduces ghosts.

However, the current pre-stack deghosting methods based on the joint deconvolution algorithm have some disadvantages.

First, the time for obtaining intermediate results may be long.

Second, the methods require accurate knowledge of the velocity field.

The joint deconvolution algorithm yields a better result if migrated data is used, but migrating the data is another time-consuming intermediate step.

However, these methods can be applied only before migration, and, although faster than the joint deconvolution algorithm, these methods have an implicit limitation for some processing stages, such as, velocity analysis or intermediate QC stacks.

In these conventional methods, the whole dataset has to be deghosted simultaneously, which is a major drawback when there is a large amount of data.

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